This invention relates to grain conveyors. More particularly the invention relates to en masse grain conveyors with chain return supports.
An en masse conveyor will typically comprise an elongate trough with a roller chain looped between a first sprocket at one end of the trough and a second sprocket at the opposite end. Grain is deposited in an inlet region adjacent the first sprocket and is discharged from an outlet region below the second sprocket. A plurality of paddles attached to the roller chain at spaced intervals extend across the trough for moving the grain. The lower section of the looped chain travels from the first sprocket to the second sprocket and moves grain en masse by the paddles toward the second sprocket. The paddles slide along the bottom of the trough providing support for the lower section of the roller chain. The upper chain return section completes the chain loop and returns the chain to the first sprocket.
The chain return section requires support intermediate the sprockets to minimize sagging and excess tension in the chain. Such en masse conveyors can have capacities ranging from hundreds to tens of thousands of bushels per hour and can vary in length up to several hundred feet. Consequently, the chain lengths can be extensive. Such conveyors are typically driven by electric motors with horsepower ratings that may exceed 100 hp for high capacity en masse conveyors. In such conveyors, a suitable low friction return section can be critical to support the efficient operation of the conveyor. Such sagging and tension can have several negative effects including excessive chain and sprocket wear along with a reduction of the conveying capacity of the conveyor. These problems are exacerbated as the capacities or the length of the conveyor increases.
Two prior art means of providing chain return supports for en masse conveyors are depicted in FIGS. 1A, 1B, 2A and 2B. Two en masse conveyors portions are depicted in FIGS. 1A and 2A, each with a trough 10, a lower chain section 12, paddles 13, an upper return section 14, and chain return supports 15, 16. FIGS 1B and 2B are end views of the chain return supports of FIG. 1A and 2A. The chain return support of FIGS. 1A and 1B is comprised of a horizontal shaft 17 supporting a plastic roller 18. An appropriate number of shafts and plastic rollers are utilized to support the channel iron along the length of the chain return section 14.
The chain return support of FIGS. 1A and 1B has drawbacks associated with the limited support points and the distance between the supports. Sagging between shaft and roller members can still be a concern and wear of the roller can also be excessive requiring more frequent maintenance.
FIGS. 2A and 2B depict a chain return support comprised of a channel iron 22 supported by a cross member or shaft 24 with a strip of plastic 21 riveted or screwed to the channel iron 22. An appropriate number of shafts are utilized to support the channel iron along the length of the chain return section 12. Collars or stops 28 are used to center the channel iron on the shaft. This support has also been used in prior art conveyors without the plastic strip. However, this results in undesirable metal to metal contact between the chain and the support and resultant excess wear and noise generation.
Ultra high molecular weight (UHMW) polyethylene plastic is suitably used for the surfaces contacted by the return chain section. UHMW plastic offers a very low coefficient of friction, causes virtually no wear to the metal parts of the roller chain, provides low noise generation, is inexpensive and is easily fabricated. UHMW does have relatively high temperature expansion and contraction characteristics, particularly compared to steel.
These temperature characteristics of UHMW plastic when attached to the steel channel iron can create problems in the chain return support configuration shown in FIGS. 2A and 2B. The rivets or bolts have not provided a satisfactory means of connecting the plastic strip 26 to the channel iron 22. The different expansion and contraction rates cause problems such as the strip 26 separating from the channel iron 22, the strip tearing or fracturing at the rivets or screws, bowing and cupping of the strip.